1. Field of the Invention
The present invention relates to methods of treating treatment objects containing harmful compounds. More specifically, the present invention relates to a method of treating treatment objects such as soil and water contaminated with harmful compounds containing arsenic (As), antimony (Sb) or selenium (Se).
2. Description of Related Art
The toxicity of an arsenic compound depends greatly on its type. Inorganic arsenic compounds typified by arsenious acid are highly toxic, while organic arsenic compounds are relatively less toxic. Inorganic arsenic compounds are methylated in human bodies and eliminated therefrom. This reaction is considered as a detoxification mechanism of living bodies.
Various methods have been proposed to detoxify inorganic arsenic compounds in the environment. The present inventor also has proposed a detoxification method for inorganic arsenic compounds using titanium oxide as a photocatalyst (JP 2009-112403 A). In this method, acetic acid, methanol, or the like is used as the source of radicals such as methyl radicals. Photocatalytic action of titanium oxide causes inorganic arsenic compounds to react with methyl radicals, etc. and to be converted into organic arsenic compounds such as dimethylarsonic acid (DMA) and arsenobetaine (AsB).